1. Field of the Invention
The present invention relates to a driving circuit for a flat panel display device and particularly, to a driving circuit for a flat panel display device which compensates luminosity deviation according to a panel characteristic an organic electroluminescent display device.
2. Description of the Background Art
FIG. 1 is a view showing a conventional driving circuit for an electroluminescent (EL) display device.
As shown in FIG. 1, the conventional driving circuit for the organic EL display device includes a current control circuit 2 for supplying constant current I0 to an organic EL display device 1 and a switching circuit 3 for switching the constant current I0 supplied from the current control circuit 2 to the organic EL display device 1.
On the other hand, FIG. 2 is a view showing a graph of a constant current IEL supplied to the organic electroluminescent display device and a voltage of both ends VEL of organic electroluminescent display device 1 according to time T. At this time, Ith and Vth designate critical values with which the organic EL display device 1 emits.
Therefore, in the conventional organic EL display device, the switch circuit 3 is turned on for the time of xcex94d and the constant current IEL is supplied from the current control circuit to the organic EL display device 1. Accordingly, The voltage VEL of both ends of the organic EL display device 1 is increased and when the voltage VEL surpasses the critical value, the organic EL display device 1 becomes to emit light. At this time, the luminosity of the light emitted from the organic EL display device 1 is determined by the size of the electric current supplied to the organic EL display device 1 and the time for supplying the current. Namely, for generating light having a uniform luminosity, the size of the electric current supplied to the organic EL display device 1 and the time for supplying the current must be uniform. However, generally, since the light-emitting characteristic of the organic EL display device 1 is differentiated according to the panel, light having a uniform luminosity cannot be generated even if an electric current is supplied uniformly in a predetermined size of the electric current and time for supplying the current. The operation will be described with reference to FIG. 3.
FIG. 3 is a graph showing luminosity deviation of respective organic EL display devices at the time that luminescence of the respective organic EL display device is ended.
As shown in FIG. 3, luminosity deviation according to the organic EL display devices is generated at the time Te that luminescence is ended. The luminosity deviation is generated by circuits dependent upon the panel and to prevent the deviation, individual driving circuits according to the characteristics of the panels must be used. However, generally, since designation of a circuit is manufacturing an integrated semiconductor chip, the manufacturing is difficult and increase the manufacturing cost. Also, in case of using the individual driving circuit, the circuit must be re-designed when the luminosity deviation is generated.
As described above, with the convention art, it was difficult that the manufacturing of the driving circuit of the organic EL display device for preventing the luminosity deviation of the organic EL display device.
Also, with the conventional art, the manufacturing cost increases in manufacturing the driving circuit of the organic EL display device for preventing the luminosity deviation of the organic EL display device.
Also, with the conventional art, the circuit must be redesigned when the luminosity deviation is generated also in case individual driving circuits are used for the organic EL display device.
Therefore, the present invention provides a driving circuit for a flat panel display device, which can compensate luminosity deviation according to panel characteristics of a flat display device.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a driving circuit for a flat panel display device including a current control circuit for supplying electric current to a panel of a flat display device, a luminescence time detecting circuit for detecting luminescence time of the flat display device and a digital signal processing circuit for controlling the current control circuit on the basis of the luminescence time.
The foregoing and other, features, aspects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.